async delete

Author: dumbbell

deps/rabbit/src/rabbit_amqqueue_process.erl

@@ -352,18 +352,41 @@ terminate_delete(EmitStats, Reason0, ReplyTo,
                                                 fun() -> emit_stats(State) end);
            true      -> ok
         end,
-        %% This try-catch block transforms throws to errors since throws are not
-        %% logged. When mnesia is removed this `try` can be removed: Khepri
-        %% returns errors as error tuples instead.
-        Reply = try rabbit_amqqueue:internal_delete(Q, ActingUser, Reason0) of
-                    ok ->
-                        {ok, Len};
-                    {error, _} = Err ->
-                        Err
-                catch
-                    {error, ReasonE} -> error(ReasonE)
-                end,
-        send_reply(ReplyTo, Reply),
+        case ReplyTo of
+            none ->
+                %% No processes are waiting for this queue process to exit. We
+                %% can handle the deletion of the queue record asynchropously.
+                %%
+                %% For instance, this allows an auto-delete queue process to
+                %% exit, even if there is a network partition preventing any
+                %% update to the metadata store when Khepri is used.
+                %%
+                %% Even if the async delete times out, the "leaked" queue
+                %% record will be cleaned up when the partition is solved (or
+                %% this node is removed from the cluster). Indeed, when the
+                %% partition is solved, all nodes are notified with the
+                %% `node_up' message from `rabbit_node_monitor'. This calls
+                %% `rabbit_amqqueue:on_node_up/1' which will delete any
+                %% transient queues.
+                _ = spawn(fun() ->
+                                  rabbit_amqqueue:internal_delete(
+                                    Q, ActingUser, Reason0)
+                          end);
+            _ ->
+                %% This try-catch block transforms throws to errors since
+                %% throws are not logged. When mnesia is removed this `try`
+                %% can be removed: Khepri returns errors as error tuples
+                %% instead.
+                Reply = try rabbit_amqqueue:internal_delete(Q, ActingUser, Reason0) of
+                            ok ->
+                                {ok, Len};
+                            {error, _} = Err ->
+                                Err
+                        catch
+                            {error, ReasonE} -> error(ReasonE)
+                        end,
+                send_reply(ReplyTo, Reply)
+        end,
         BQS1
     end.